Virtually all constitutions codify amendment rules. But why? What are the uses and purposes of constitutional amendment rules? Amendment rules of course create a legal process for reformers to alter the constitution. But amendment rules serve important purposes even if the constitution is never amended at all because they have essential uses beyond the obvious one of textual alteration. Amendment rules have three categories of uses: formal, functional, and symbolic. Their formal uses include repairing imperfections, distinguishing constitutional from ordinary law, entrenching rules against easy repeal or revision, and establishing a predictable procedure for constitutional change. Their functional uses include checking the court, promoting democracy, heightening public awareness, pacifying change, and managing difference. Symbolically, amendment rules can be used to express constitutional values. This chapter explains all of these many uses of amendment rules and illustrates each of them with examples drawn from constitutions around the world. This chapter also interrogates the symbolic uses of amendment rules: How can we know whether the values expressed in constitutional amendment rules reflect authentic political commitments? This chapter explains with reference to the German Basic Law that it is possible to evaluate the authenticity of the values in amendment rules by investigating the design of amendment rules and their subsequent interpretation. This chapter considers constitutions from Afghanistan, Albania, Algeria, Bosnia and Herzegovina, the Central African Republic, Chad, China, Cuba, Ecuador, Germany, Kazakhstan, Kiribati, Saint Lucia, South Africa, Spain, the Russian Federation, the Soviet Union, Ukraine, the United States, and Yugoslavia.